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During groundwater recharge with reclaimed water, pentabromodiphenyl ether (BDE-99) might contaminate the underground aquifers. In order to understand the effects of elevated sulfate concentrations on the biodegradation of BDE-99, lab-scale column experiments were performed to study the changes in bacterial and archaeal communities. The results confirmed that the biodegradation rate of BDE-99 improved significantly with the addition of sulfate. Oxygen was replaced by sulfate as the predominant electron acceptor, and the major biodebromination metabolites of BDE-99 were BDE-28 and BDE-47, respectively, The results from 454 pyrosequencing of 16s rRNA genes showed that the microbial community structure shifted toward communities with BDE-99 co-metabolism ability. At the bacterial genus level, Geothrix , Thiobacillus , Sphingomonas , Paenibacillus and Desulforhabdus were the five most abundant genera, wherein, Thiobacillus was able to treat the toxic products generated during polybrominated diphenyl ethers (PBDE) biodegradation. In the case of archaea at the genus level, Methanobrevibacter , Methanomethylovorans , DHVEG-6, Candidatus Nitrososphaera and Methanosphaera were the predominant groups, of which Methanobrevibacter and Methanosphaera showed good ability to metabolize BDE-99 with sulfate amendment. [ABSTRACT FROM AUTHOR]

The use of tertiary-treated municipal wastewater for groundwater recharge through river utilization may cause pentabromodiphenyl ether (BDE-99) pollution, which poses a potential risk to groundwater aquifers. Elevated nitrate levels may change the structure of microbial communities, thus influencing the biodegradation of BDE-99. To investigate the influence of elevated nitrate levels on the changes in microbial communities and associated biodegradation of BDE-99 appropriately, a laboratory-scale column was designed to simulate the percolation process. The results showed that the attenuation rate of BDE-99 increased with nitrate concentrations. The lower-brominated ether congeners were the primary debrominated metabolites, while high-brominated diphenyl ethers and isomers of BDE-100 also emerged, and their concentrations decreased with reduced nitrate concentrations. The microbial community composition and structure significantly changed with elevated nitrate levels and relative abundance of nitrate-reducing bacteria with diverse metabolic capabilities increased. The order of the relative abundance of the largest five classes, as well as the relative abundances of the largest five families and genera, changed with increasing nitrate concentrations. The diversity of microorganisms with universal aromatics-degrading abilities related to nitrogen transformation played an important role in mitigating the infiltration of BDE-99 to groundwater. [ABSTRACT FROM AUTHOR]

In this long-term field study, to restore a dried river ecosystem, reclaimed water was used as a supplementary water source. The main aim of this study was to investigate the accumulation and migration potential of EDCs in groundwater during long-term utilization of reclaimed water and the changes in microbial community during the removal of EDCs. A long-term field study was conducted in order to ascertain the temporal and spatial distribution of four selected endocrine-disrupting chemicals (EDCs) in an underground aquifer in the Chaobai watershed, where reclaimed water is the primary water source. Anew, the microbial community structure at different groundwater depths, along with related environmental factors were also determined. Based on the results obtained from this long-term study, it was found that the EDCs in the surface water of the Chaobai river have entered a depth of 80 m in the groundwater aquifers, within a distance of 360 m from the river. The vertical profiles of the concentrations of bisphenol A (BPA), 4-nonylphenol (NP), estrone (E1), and estriol (E3) decreased significantly from the surface to different groundwater depths with first-order attenuation rates of 0.0416, 0.0343, 0.0498, and 0.0173 m-1. The aquifer depth, water temperature, conductivity, and coexisting anions correlated well with the distribution of EDCs in groundwater. • Spatiotemporal variation of 4 endocrine disrupting chemicals (EDCs) was ascertained. • Analysis of variance (ANOVA) were used to perform statistical analysis of the data. • EDCs in groundwater depends on aquifer depth, temperature, competing ions, etc. • Microbial communities and their clustering affected the degradation of EDCs. • Microorganisms affected by: temperature > depth > EDC concentration > pH > TOC. [ABSTRACT FROM AUTHOR]